With the realization of high-speed semiconductor devices miniaturization of wiring patterns, Cu is attracting attention as a wiring material, for it has higher conductivity than aluminum as well as high electromigration tolerance. As a method for forming a Cu film, there has been known a chemical vapor deposition (CVD) method of forming a Cu film on a substrate by a pyrolysis reaction of a source gas containing Cu or by a reduction reaction between the source gas containing Cu and a reducing gas. A Cu film formed by this CVD method is suitable for forming fine wiring patterns because it has high coverage as well as high infiltration in a deep and narrow pattern.
With regard to various thin film forming processes using the CVD method, there has been proposed increasing a substrate temperature as a method to improve a film forming rate (see, for example, Japanese Patent Laid-open Application No. 2002-151488 (paragraphs 0002, 0003, etc.). However, if the temperature of the substrate is set to be high when a Cu film is formed, it would result in an agglutination of the Cu film.